The MIL-STD-810F test series, approved for use by all departments and agencies of the United States Department of Defense (DoD), emphasizes tailoring an environmental design and test limits to the conditions that it will experience throughout its service life.
A US-based Gumstix customer passed US MIl Spec 810.F tests for both shock and vibraton with an Overo IronSTORM COM, custom expansion board and flex ribbon cable connection.
These test results prove the robustness of the dual 70-pin connectors and the 27-pin connector of the Overo COM mechanical design.
The Overo COM and the expansion board were secured together using Gumstix' white retaining spacers 48 / 48.
Their configuration of "ground equipment" consisted of the following components:
- an Overo IronSTORM COM connected to their custom expansion board via the dual 70-pin connectors.
- a flex ribbon cable running from a TI video encoder chip on the custom expansion board up to the 27-pin camera connector (J5) on the Overo COM.
- Ensure that the flex cable goes into the 27-pin connector flat and level and that the flex cable remains flat and level during operation.
- Use each white ribbon cable for a maximum of ten cycles, only. One cycle = an insertion and removal to the 27-pin connector.
MIL-STD 810F Method 514.5 Vibration (constant acceleration) - Passed
MIL-STD 810F Method 516.5 Shock - Passed. Note, this testing included "40G jolts while running", according to the customer.
In Use Experience:
March 2012: Some customer experiences regarding the reliability of the Overo series have been openly discussed on the Gumstix communtiy mailing list, such as this thread titled overo com reliability.
- "We have had a little over 200 Overo COMs out in public transport vehicles (buses and ferries) since May 2009. We have had zero failures. The environment is quite harsh with units being switched on/off several times a day with no shut-down procedure and operational spikes of over 40C ambient (buses parked in direct sunlight with AirCon switched off". This Gumstix customer originally reported the testing results above.
- This mailing list discussion concluded with this posting by Mark Meisner, also a Gumstix customer:· "After researching the reliability issues further we’ve found that the few identified issues have been already been addressed and are no longer open issues.·Therefore, we have concluded to continue to move forward with the development of our project with full confidence in the Gumstix platform".
The tests performed by this Gumstix customer simulated vibration for the equivalent of 1,642,500 kilometers, which is the average distance a bus travels in 5 years making this testing an accelerated simulation of a “Diesel Engine Road Vehicle” running over an assortment of road surfaces. Essentially, an hour of simulation equates to a number of kilometres travelled.
- Their Overo COM and Tobi expansion board configuration passed the 5 year, MIL-STD-810F 514.5·military test for·Vibration (constant acceleration).This extended test result was completed successfully because the customer engineers secured the Gumstix Overo and Tobi boards together with the·retaining spacers supplied by Gumstix and gluing the configuration together. This extra mechanical connection was deemed to have reduced board flexing.
- Their Overo COM and expansion board combination passed the 2-3 year, MIL-STD-810F 514.5 mark without the addition of retaining spacers, gluing or screws.
Further commentary from the customer:
- The testing done by this customer is extremely harsh.
- The customer stated that "the design and robustness of the Gumstix Overo series without the retaining spacers is extremely high and under normal circumstances are fit for purpose" and "that they "don’t believe that any units would have actually failed in the field".
- The customer tested 3 Gumstix Overo units: one announcement unit, one tracking unit and an Overo Earth/Summit combination. All three configurations complied with this MIL-STD-810F standard until approximately the 2 – 3 year mark. Under strobe light/vibration observations without spacers, the customer could see the U8 end of the Overo flexing at resonant frequencies.
The customer reported that this flexing does not happen to the Overo COM when the retaining spacers are fitted. The customer believes that this ‘flexing’ is causing small amounts of wear to the plug/sockets that eventually leads to failure at the 2-3 year mark when cycled under this accelerated simulation.